1. Questions

calculus

Could someone help me et up this problem?

Two people start from the same point. one walks east at 3mi/h and the other walks northeast at 2mi/h. How fast is the distance between the poeple changing after 15 minutes?

I think this is what I would do:::

First I would set up a triangle:

hypotenuse=h (northeast walking person)
height=y
leg=x (north walking person)

GIVEN: dx/dt=3mi/h
dh/dt=2mi/h

Need to find dy/dt when t=15.

  1. 👍
  2. 👎
  3. 👁
  4. ℹ️
  5. 🚩
Anonymous

  1. East problem
    East walker at 3 mi/hr
    NE walker at 2 cos 45 mi/hr
    East distance between = (3 -1.41)t = 1.59 t
    North distance between = 1.41 t
    h = hypotenuse = t sqrt(1.59^2 + 1.41^2)
    = 2.13 t
    now find dh/dt
    dh/dt = 2.13 mi/hr

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
    Damon

  2. your work doesn't match the wording of the question.
    Where does it mention a north-walking person? (your x)
    There isn't even a right angled triangle

    I drew a horizontal line to the east (to the right)
    then from the same starting point a line at 45º to the other one (going north-east)
    (make the horizontal a little longer, it represents 3 mph)

    let the distance between their endpoints be x
    let the time after they both leave be t hours.
    then the 'going-east' line has length 3t
    the 'north-east' line is 2t

    by Cosine Law
    x^2 = (3t)^2 + (2t)^2 - 2(3t)(2t)cos 45º
    = 13t^2 - 12t^2cos45
    = 13t^2 - 6√2 t^2
    dx/dt = 26t - 12√2t

    when t = 15 min = 1/4 hour
    dx/dt = 26(1/4) - 12√2(1/4)
    = 2.26 mph

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
    Reiny

  4. thanx I thought I had to use the cosine law but I wasn't quite sure how to.

    But how did you decide that the angle would be 45 degrees?

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
    Anonymous

  5. where does a direction of North-East go in relation to East ?
    What is the angle between North and East?

    1. 👍
    2. 👎
    3. ℹ️
    4. 🚩
    Reiny

Respond to this Question

First Name

Your Response

Similar Questions

  1. Physics(Please respond)

    A 12-kg crate is pushed up an incline from point A to point B. What is the change in the gravitational potential energy of the crate? Point A is 2.0m and point b is 7.0m I am not sure how to start this.

  2. Math

    Write a rule for the sequence 2,6,10,14 A.start with 2 and subtract 4 repeatedly B. Start with 4 and add 2 repeatedly C. Start with 2 and add 4 repeatedly ▶D. Start with to and add one add to at 3 and so on 2,4,8,16 A. Start

  3. Operations with Radical Expressions

    Operations with Radical Expressions 1. Simplify the expression: 4 times Start Root 18 End Root plus 5 times Start Root 32 End Root (1 point) 45 times the square root of 2 32 times the square root of 2👈 116 times the square root

  4. College Physics

    A point charge of 1.8 uC is at the center of a Gaussian cube 55 cm on edge. What is the net electric flux through the surface? I have no idea where to start with this problem.

  1. Math

    Find the product. Your answer should be in simplest form. 1. one-third• 7 (1 point) one over twenty-one two and one-seventh two and one-thirdFind the product. Your answer should be in simplest form. 2. –seven-ninths• start

  2. economics

    wireless high speed internet is provided for free in the airport of the city of communityville a)At first, only a few people use the service. What type a good is this and why? b) Eventually, as more find out about the service and

  3. math

    Solve each problem and write your answers in scientific notation. 1. (6.0 x 105) x (3.0 x 104) = (1 point) 18 x 1020 18 x 109 1.8 x 1020 1.8 x 1010 2. (5 x 10–2) ÷ (2 x 103) = (1 point) 2.5 x 10-5 2.5 x 10-1 25 x 101 25 x 102

  4. Minnesota Studies 6 B

    1. Why were Nisei kept in internment camps? (1 point) They were prisoners of war. They refused to work and support the war. People feared they were spies. People worried that they did not have enough rations to share.

  1. Algebra

    A catering company charges a $300.00 set up fee and $10.00 per person for a lunch buffet. Approximately how many people must attend the lunch so that the total cost per person is $14.00? (1 point) • 75 people • 30 people •

  2. Calculus

    Two people start from the same point. One walks east at 5 mi/h and the other walks northeast at 7 mi/h. How fast is the distance between the people changing after 15 minutes? (Round your answer to three decimal places.)

  3. math

    1. Write a rule for the sequence. 3, –3, –9, –15, . . . (1 point) Start with 3 and add –6 repeatedly. Start with –6 and add 3 repeatedly. Start with 3 and add 6 repeatedly. Start with 3 and subtract –6 repeatedly. 2.

  4. STATS

    Solve the problem. Round the point estimate to the nearest thousandth. 22 randomly picked people were asked if they rented or owned their own home, 9 said they rented. Obtain a point estimate of the proportion of home owners. A)

View more similar questions or ask a new question.